The present invention relates generally to shaft seal systems, and more particularly to a novel seal system for a shaft which extends between two regions containing different fluids which are to be isolated from each other.
In U.S. Pat. No. 3,887,197, a seal system is disclosed which finds application in isolating two regions containing different fluids and between which a rotating shaft extends. As therein set forth, one such application is the isolation of a reactor coolant, such as helium or carbon dioxide, within a fluid circulator chamber in the primary containment vessel of a nuclear reactor wherein the circulator is powered by the shaft of a turbine driven by a fluid, such as steam or water, which must be isolated from the reactor coolant. An example of such a fluid circulator is illustrated and described in U.S. Pat. No. 3,520,640.
In the seal system of U.S. Pat. No. 3,887,197, a seal housing is provided through which a stepped cylindrical rotating shaft extends and which defines an annular land and an annular labyrinth facing on the shaft so that each establishes a fluid sealing annulus or space with the shaft. A collection cavity in the seal housing communicates with both annular sealing spaces so that fluids, such as water and helium gas, compatable with the respective fluid regions to be isolated may be passed through the annular sealing spaces into the collection cavity from which the water and gas fluids are passed to a separator and recycled for sealing purposes. In the disclosed seal system, gas reactor coolant from the circulator is passed through a gas purifier from which the gas is introduced into the labyrinth sealing space by a pressure pump to provide an isolating fluid seal which prevents flow of liquid or liquid moistened gas into the circulator chamber. It will be appreciated that should the pump which pumps sealant gas into the labyrinth sealing annulus malfunction or otherwise become temporarily disabled, liquid moistened gas might enter into the circulator chamber with adverse results.